In the manufacturing process of a Thin Film Transistor Liquid Crystal Display (TFT-LCD), Electro-Static Discharge (ESD) protection has always been an important research subject. Static electricity is a major factor only second to particle affecting the production rate. Whether the solution to the ESD problem is good or not may directly affect the enterprise benefits.
Electro-static discharge is a phenomenon of electrostatic charges transferring between different objects due to electro-static accumulation. Electro-static discharge occurs within a very short period, a large amount of current is generated within such a short period, and the large amount of current generally damages a semiconductor integrated circuit once flowing through the semiconductor integrated circuit to cause electro-static damage. The electro-static damage is a common phenomenon and may lead to breakdown of an insulating medium so as to cause threshold voltage shift or short circuit between a gate electrode and source and drain electrodes. For a thin film transistor device such as a TFT-LCD, the electro-static damage is more liable to occur in the manufacturing process because a thin film transistor (TFT) is formed on an insulating substrate glass and electrode charges are easily accumulated to a higher voltage level. When the electro-static accumulation reaches a certain extent, an insulating medium film used for separating the gate electrode from the source and drain electrodes is likely to generate breakdown so as to cause short circuit of the source electrode and the gate electrode. Even if the insulating medium generates no breakdown, the accumulated static electricity shall cause voltage difference between the gate electrode and the source electrode to lead to TFT threshold voltage shift to change the TFT working property. Unless there is a proper discharge path, otherwise when the electro-static charges are randomly discharged after being accumulated to a certain degree, a part of the pixel structures may be broken to cause poor display or even damage of the whole liquid crystal display.
A lot of researches have been made to prevent electro-static damage in the TFT-LCD industry. Now a consensus has been basically formed that electro-static damage is associated with production equipment. Electro-static damage often occurs in the transport and disposal processes of glass substrates and in the manufacturing process of the TFT-LCD, for example, the electro-static discharges are likely to occur on the glass substrates in a thin film deposition process or a thin film etch process or any other process. With the increase of requirements on the production level and production efficiency of the TFT-LCD, the size of the glass substrate of the TFT-LCD becomes larger and larger, and the transportation and disposal speeds of the glass substrate are faster and faster. These changes have increased the risk of electro-static discharge damage. With the increase of the requirements on large-size LCD TVs, the sizes of the TFT-LCD devices are gradually decreased, for example, the width of a metal line is decreased to reduce parasitic capacitance. These changes on the structures of the thin film transistor devices result in easier electro-static discharge damage in the TFT-LCD manufacturing process.
Therefore, how to effectively improve the antistatic ability of the panel on the condition of not affecting the effective display region is a technical problem to be urgently solved by those skilled in the art.